At 04:38 AM 1/23/97 -0800, Tim Bray wrote:
I then
>believed, and still do, strongly, that it would be useful for there
>to be a standard way for an object to assert "Here is the canonical
>address which I request to be used in retrieving the object you are now
>reading". Use in hot-lists and by crawlers being just two obvious
>applications. I think this would be a highly useful, cheap-to-specify,
>easy-to-implement item to put in XML-LINK.
>
>Any reason not to do this? - Tim
The only time I can see this being a problem is when an object *doesn't
have* a cannonical position, or the one it has changes frequently. But
even then, you can use indirection (e.g., FPIs or URNs) to hide the change
in actual location.
I know the issue of putting document's public indentifiers inside them has
been discussed in some forum in the past (I dimly remember discussing it
with Steve DeRose). One problem with SGML is that document entities are
not self describing in that they don't normally carry their own canonical
names with them (i.e., their public identifiers). Thus, you must always
have some other object that catalogs documents (i.e., a document management
system, even if it's only an SGML Open catalog that lists all the documents
in the "system". Of course, when the system is unbounded, that's a bit
difficult.
Let me add to this question: should the SGML standard add syntax to bind
document entities to their external identifiers (which would, by the
definition of external identifier, include both system IDs (and thus,
potentially, URLs or URNs) and publid identifiers)?
Cheers,
E.
--
W. Eliot Kimber (eliot@isogen.com)
Senior SGML Consulting Engineer, Highland Consulting
2200 North Lamar Street, Suite 230, Dallas, Texas 75202
+1-214-953-0004 +1-214-953-3152 fax
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